I don't have a lot of room to talk, regardless what I do it seems I still have areas that don't completely sand out too in my furniture. But wetting it down has helped me see them more than anything. I will wipe (wood) down with lacquer thinner. That will usually bring out the scratch marks. A light down low shinning across the wood, not down on it and a low vantage point will help.

I just finished a hard maple butcher block style bench top that I salvaged. Had to belt sand it down to get past the imperfections. I knew it had some serious marks in it. I was careful I thought. But once the finish went on I could see spots I missed when sanding it. It is in my kitchen and eat off it and it bugs me big time!! So I know the feeling all to well.